Time guilt...

why when I take time for me do I always feel compelled to squeeze in mom duty stuff and then feel so guilty for leaving my kids too long with the grandparents? they watched them sat afternoon for me so i could go exercise and get some groceries...i ended up doing those things and grabbed a mani/pedi to boot....i told them it was going to be like 2 hours or so but it ended up being just over 3 and i got panicked that they were going to be annoyed i was taking too long, even though they both told me they didn't have plans and when i checked in reassured me that the kids were fine, not to worry.....They are so wonderful in offering to watch the kids and take them pretty much whenever i ask, so I'm not sure why i always worry that I'm having the kids overstay their welcome so to speak....i guess i just have to work on letting it go as it seems mommy guilt just comes with the job, not really any way to avoid it overall....